The present invention relates generally to filtering devices and systems which can be used when an interventional procedure is being performed in a stenosed or occluded region of a body vessel to capture embolic material that may be created and released into the vessel during the procedure. The present invention is more particularly directed to deployment and recovery control systems which can be used in conjunction with such embolic filtering devices. The present invention is particularly useful when an interventional procedure, such as balloon angioplasty, stenting procedures, laser angioplasty or atherectomy, is being performed in a critical body vessel, such as the carotid arteries, where the release of embolic debris into the bloodstream can occlude the flow of oxygenated blood to the brain, resulting in grave consequences to the patient. While the recovery and deployment systems of the present invention are particularly useful in carotid procedures, the inventions can be used in conjunction with any vascular interventional procedure in which an embolic risk is present.
Numerous procedures have been developed for treating occluded blood vessels to allow blood to flow without obstruction. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient""s arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel, resulting in increased blood flow. The balloon is then deflated to a small profile so that the dilatation catheter can be withdrawn from the patient""s vasculature and the blood flow resumed through the dilated artery. As should be appreciated by those skilled in the art, while the above-described procedure is typical, it is not the only method used in angioplasty.
Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which cutting blades are rotated to shave the deposited plaque from the arterial wall. A vacuum catheter is usually used to capture the shaved plaque or thrombus from the blood stream during this procedure.
In the procedures of the kind referenced above, abrupt reclosure may occur or restenosis of the artery may develop over time, which may require another angioplasty procedure, a surgical bypass operation, or some other method of repairing or strengthening the area. To reduce the likelihood of the occurrence of abrupt reclosure and to strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, commonly known as a stent, inside the artery across the lesion. The stent can be crimped tightly onto the balloon portion of the catheter and transported in its delivery diameter through the patient""s vasculature. At the deployment site, the stent is expanded to a larger diameter, often by inflating the balloon portion of the catheter.
The above non-surgical interventional procedures, when successful, avoid the necessity of major surgical operations. However, there is one common problem which can become associated with all of these non-surgical procedures, namely, the potential release of embolic debris into the bloodstream that can occlude distal vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible that the metal struts of the stent can cut into the stenosis and shear off pieces of plaque which become embolic debris that can travel downstream and lodge somewhere in the patient""s vascular system. Pieces of plaque material can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become released into the bloodstream. Additionally, while complete vaporization of plaque is the intended goal during laser angioplasty, sometimes particles are not fully vaporized and thus enter the bloodstream. Likewise, not all of the emboli created during an atherectomy procedure may be drawn into the vacuum catheter and, as a result, enter the bloodstream as well.
When any of the above-described procedures are performed in the carotid arteries, the release of emboli into the circulatory system can be extremely dangerous and sometimes fatal to the patient. Debris that is carried by the bloodstream to distal vessels of the brain can cause these cerebral vessels to occlude, resulting in a stroke, and in some cases, death. Therefore, although cerebral percutaneous transluminal angioplasty has been performed in the past, the number of procedures performed has been limited due to the justifiable fear of causing an embolic stroke should embolic debris enter the bloodstream and block vital downstream blood passages.
Medical devices have been developed to attempt to deal with the problem created when debris or fragments enter the circulatory system following vessel treatment utilizing any one of the above-identified procedures. One approach which has been attempted is the cutting of any debris into minute sizes which pose little chance of becoming occluded in major vessels within the patient""s vasculature. However, it is often difficult to control the size of the fragments which are formed, and the potential risk of vessel occlusion still exists, making such a procedure in the carotid arteries a high-risk proposition.
Other techniques include the use of catheters with a vacuum source which provides temporary suction to remove embolic debris from the bloodstream. However, as mentioned above, there can be complications associated with such systems if the vacuum catheter does not remove all of the embolic material from the bloodstream. Also, a powerful suction could cause trauma to the patient""s vasculature. Still other techniques which have had some limited success include the placement of a filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. The placement of a filter in the patient""s vasculature during treatment of the vascular lesion can reduce the presence of the embolic debris in the bloodstream. Such embolic filters are usually delivered in a collapsed position through the patient""s vasculature and then expanded to trap the embolic debris. Some of these embolic filters are self expanding and utilize a restraining sheath which maintains the expandable filter in a collapsed position until it is ready to be expanded within the patient""s vasculature. The physician can retract the proximal end of the restraining sheath to expose the expandable filter, causing the filter to expand at the desired location. Once the procedure is completed, the filter can be collapsed, and the filter (with the trapped embolic debris) can then be removed from the vessel. While a filter can be effective in capturing embolic material, the filter still needs to be collapsed and removed from the vessel. During this step, there is a possibility that trapped embolic debris can backflow through the inlet opening of the filter and enter the bloodstream as the filtering system is being collapsed and removed from the patient. Therefore, it is important that any captured embolic debris remain trapped within this filter so that particles are not released back into the body vessel. Additionally, the recovery apparatus should be relatively flexible to avoid straightening of the body vessel. Recovery devices which are too stiff can cause trauma to the vessel walls as the filter is being collapsed and removed from the vasculature.
Some prior art expandable filters vessel are attached to the distal end of a guide wire or guide wire-like tubing that allows the filtering device to be placed in the patient""s vasculature as the guide wire is steered by the physician. Once the guide wire is in proper position in the vasculature, the embolic filter can be deployed to capture embolic debris. Some embolic filter devices which utilize a guide wire for positioning also utilize the restraining sheath to maintain the expandable filter in a collapsed position. Once the proximal end of the restraining sheath is retracted by the physician, the expandable filter will move into its fully expanded position within the patient""s vasculature. The restraining sheath can then be removed from the guide wire allowing the guide wire to be used by the physician to deliver interventional devices, such as a balloon angioplasty dilatation catheter or a stent delivery catheter, into the area of treatment. After the interventional procedure is completed, a recovery sheath can be delivered over the guide wire using over-the-wire techniques to collapse the expanded filter for removal from the patient""s vasculature. As mentioned above, the recovery device, i.e., the recovery sheath, should be relatively flexible to track over the guide wire and to avoid straightening the body vessel once it is in place.
When a combination of an expandable filter and guide wire is utilized, it is important that the guide wire be rotatable so that the physician can steer it downstream of the area of treatment using techniques well known in the art. In this regard, the guide wire is usually xe2x80x9ctorquedxe2x80x9d by the physician to point or steer the distal end of the guide wire into the desired body vessel. Often, when the restraining sheath is utilized, it is difficult to properly turn the composite device to deliver the filter through the tortuous anatomy of the patient. Moreover, during delivery, it is imperative that the restraining sheath remain positioned over the collapsed filter, otherwise the filter could be deployed prematurely in an undesired area of the patient""s vasculature. This occurrence can cause trauma to the walls of the patient""s vasculature and would require the physician to re-sheath the expanded filter to further advance the filter into the desired area. Moreover, if the physician does not have an adequate mechanism or handle at the proximal end of the composite filter device for steering the device through the tortuous anatomy, there can be unwanted buckling of the guide wire at the proximal end. Additionally, as the restraining sheath is being retracted, the physician has to be careful not to buckle or bend the guide wire. These types of occurrences during delivery and deployment of the embolic protection device are certainly undesirable.
What has been needed are reliable deployment and recovery control systems which can be used with embolic protection devices that minimize the above-mentioned incidents from ever occurring. These systems should be relatively easy for a physician to use and should provide failsafe systems for deploying the embolic filtering device into the desired area of the vessel and retrieving the same device without releasing any captured embolic debris into the body vessel. Moreover, such systems should be relatively easy to deploy and remove from the patient""s vasculature. The inventions disclosed herein satisfy these and other needs.
The present invention provides deployment and recovery control systems for use with embolic filtering devices and systems for capturing embolic debris created during the performance of a therapeutic interventional procedure, such as a balloon angioplasty or stenting procedure, in a body vessel. The systems of the present invention are particularly useful when an interventional procedure is being performed in critical arteries, such as the carotid arteries, in which vital downstream blood vessels can easily become blocked with embolic debris, including the main blood vessels leading to the brain. The present invention provides the physician with a deployment control system which can be used with an embolic protection device that generally includes a guide wire having a distal end, an expandable filter attached to the guide wire near its distal end, and a restraining sheath that maintains the expandable filter in a collapsed position until it is ready to be deployed within the patient""s vasculature. The recovery control system of the present invention can be used to collapse and retrieve the expanded filter once the interventional procedure has been completed. The present invention provides the physician with control mechanisms that enhance the ease of deploying and recovering the embolic protection device while providing novel features, described below which are beneficial during delivery and recovery of the embolic protection device.
The deployment control system of the present invention provides a number of benefits to the physician which include better handling of the guide wire/embolic protection device from the proximal end where the physician manipulates the guide wire for steering purposes. In this regard, the physician is better able to torque the guide wire of the embolic protection device to steer the coil tip of the guide wire into the desired body vessel during delivery. The deployment control system of the present invention also helps to prevent any premature deployment of the expandable filter which may occur by preventing the restraining sheath from being accidentally retracted during the delivery process. Moreover, the present invention provides a mechanism for preventing the guide wire from buckling as the restraining sheath is being retracted to deploy the expandable filter. The simplicity of the deployment control system of the present invention provides advantageous benefits to the physician and provides a virtual failsafe system for safely delivering and deploying the embolic protection device with the patient""s vasculature.
The recovery control system of the present invention utilizes an inner catheter which is capable of being introduced over the guide wire, along with a recovery sheath which extends co-axially over the inner catheter. The inner catheter is capable of being loaded inside a lumen of the recovery sheath. In use, a distal portion of the inner catheter extends beyond the distal end of the recovery sheath allowing the inner catheter to initially approach the expanded filter which has been deployed within the patient""s vasculature. Once the inner catheter has been placed near the expandable filter, the recovery control mechanism can be locked onto the guide wire and held stable as the recovery sheath is advanced distally over the expanded filter to collapse it for removal from the patient. In this manner, the recovery sheath is advanced over the inner catheter allowing the collapse of the expandable filter to be smoother and less likely to result in any trapped embolic debris being released back into the body vessel as the recovery sheath is advanced over the filter. The proximal ends of the inner catheter and outer restraining sheath include handle portions having snap mechanisms which holds the two components together as the components are being moved into the patient""s vasculature for recovery purposes. The proximal handles facilitate the ease in which the physician can collapse and retrieve the expandable filter from the patient""s vasculature.
The method of using the deployment control system to deliver and deploy an embolic protection device into a patient""s vasculature includes loading a deployment control system onto an embolic protection device which includes a guide wire, an expandable filter assembly located near the distal end of the guide wire, and a restraining sheath for maintaining the expandable filter in a collapsed position. The deployment control system includes a torque control device attached to the guide wire near its proximal end and a spacer member disposed between the torque control device and the proximal end of the restraining sheath. The method includes introducing the composite deployment control system/embolic protection device into the patient""s vasculature and advancing the distal portion of the embolic protection device into the desired location in the body vessel, usually downstream of an area to be treated. The spacer member can then be removed from the guide wire allowing the restraining sheath to be retracted proximally towards the torque control device in order to deploy the expandable filter assembly. In one aspect of the present invention, a wire introducer can be placed between the torque control device and the proximal end of the restraining sheath to provide a stiffening structure for the guide wire to prevent buckling or bending of the guide wire as the proximal end of the restraining sheath is being retracted back towards the torque control device. The deployment control system and recovery sheath can then be removed from the guide wire to allow interventional devices to be advanced over the guide wire into the area of treatment. Thereafter, any embolic debris created during the interventional procedure should be captured in the expandable filter which has been deployed downstream from the area of treatment.
The method of using the recovery control system to collapse and retrieve an embolic protection device includes loading the inner catheter inside a recovery sheath, wherein the recovery sheath is initially placed over the inner catheter such that a distal portion of the inner catheter extends beyond the distal end of the recovery sheath. The inner catheter recovery sheath can then be introduced over the guide wire which includes an expanded filter located near its distal end. The distal end of the inner catheter is advanced to a position adjacent to the expanded filter located within the patient""s vasculature. The inner catheter can then be hooked onto the guide wire. The recovery sheath can then be advanced over the distal portion of the inner catheter and over the expanded filter in order to collapse the expanded filter. The recovery sheath, inner sheath, guide wire and partially or completely collapsed filter can then be removed from the patient""s vasculature.
It is to be understood that the present invention is not limited by the embodiments described herein. The present invention can be used in arteries, veins, and other body vessels. Other features and advantages of the present invention will become more apparent from the following detailed description of the invention, when taken in conjunction with the accompanying exemplary drawings.